1. Sol Price School of Public Policy, Univ. of Southern California, 650 Childs Way, Los Angeles, CA 90089 (corresponding author).
2. Humphrey School of Public Affairs, Univ. of Minnesota–Twin Cities, 301 19th Ave. S, Minneapolis, MN 55455.
3. Dept. of Civil Engineering, Univ. of Minnesota–Twin Cities, 500 Pillsbury Dr. SE, Minneapolis, MN 55455.
4. San Francisco Municipal Transportation Agency, 1 S. Van Ness Ave., San Francisco, CA 94103.